The present invention refers to a device for the coupling of excavator teeth which is applicable to the buckets of excavating machines and, in general, to the active working edges of earth-moving-machines of similar types.
Machines for civil engineering work which effect the removal of materials such as earth, rocks, etc., generally have active edges on the so-called buckets of the excavators, which are open receptacles of specific shape fixed to the supporting and travelling gear of the machine and which have the function of removing the mass of earth or earth and more or less loose stones, by means of their front edge, collecting in the bucket the materials which have been loosened, allowing them to be transferred to a vehicle for their transport to another site or simply for depositing the mass of earth and stones which has been removed, for its subsequent replacement, for example, in the case of the opening of a trench.
The buckets of excavators and the like suffer significant problems at the active edge because of the high degree of wear to which it is subjected by contact with the earth and stones, which have very abrasive characteristics. For this reason, it is necessary to equip the active edge of the excavator or similar machine with detachable teeth, which are removable components which bear the greater part of the wear by being in direct contact with the mass of earth and stones, and which are therefore parts which wear out very quickly. Said teeth, which are parts that can be exchanged fairly frequently, must combine characteristics which are to a certain extent contradictory, owing to the fact that, being parts which are changed frequently on excavating machines and the like, their price should be relatively low, so it is necessary to exclude mechanization of the teeth, which should be manufactured simply by casting or forging high strength steel. The other contradictory characteristic lies in the need for the mounting of the tooth on the tooth-carrier located at the active edge of the bucket for excavators or the like to be affected with sufficient adjustment to avoid as far as possible any play between the facing regions of the tooth-carrier and the tooth, since the occurrence, otherwise inevitable, of play in the said region results in an increase in the stresses at specific points of contact between the tooth and the tooth-carrier, which further increase the wear locally, in a process which may end in breakage of the parts and which involves changing the worn part, that is to say, the tooth, more or less frequently, according to how the above-mentioned wear phenomena can be controlled to a greater or lesser degree.
At present, many types of coupling between the teeth of excavators and the tooth-carriers are known, although all of them, given the contradictory conditions to be fulfilled and the hard work to which said components are subjected, exhibit defects with regard to what could be considered an ideal solution in terms of life of the tooth and avoidance of excessive wear on the tooth-carrier, enabling the latter to have an acceptably extended life.
U.S. Pat. No. 5,561,925 refers to a tooth assembly and retaining mechanism in which a nose portion matching with the socket of the tooth has parallel surfaces interconnected by a flat end surface.
U.S. Pat. No. 4,625,439 refers to an excavating tooth retaining means comprising a nose portion in which the tooth is fixed by means of a wedge in which the wear part lands directly against the holder.
However, none of said patents discloses the double inverted dovetail structure which characterizes the present invention.
In order to obtain an improvement in the characteristics of the couplings for excavator teeth, achieving rapidity of assembly and secure and durable coupling between the tooth and the tooth-carrier, the inventor of the present patent application has carried out investigations and tests which have resulted in a coupling for excavator teeth which has an improved performance in use.
The coupling for excavator teeth and the like which is the subject of the invention is of the type which has a projection on the front face of the tooth-carrier, directed substantially axially with respect to the longitudinal axis of the tooth-carrier, and in which the cross-section of the tooth coupling region has a cross-section decreasing from the starting region to the free end, being characterized by the combination of the areas of contact between the tooth-carrier and the tooth, and the positioning of the retaining cotter pin, so that close coupling is obtained between the tooth and the tooth-carrier, giving rise to secure fastening, with many areas of contact between the two coupled components, for the purpose of reducing the local wear and with an arrangement of angles of the areas of contact such that the stresses produced on the tooth tend to produce greater wedging and matching of the tooth with the tooth-carrier. In order to obtain this result, the area coupling the tooth with the tooth-carrier has a structure which is constituted basically by the joining of two reverse dovetail profiles, that is to say, the dovetail at the first end region being inverted compared to the dovetail at the second end region, corresponding to the starting region and the free end or point of the so-called xe2x80x9cnosexe2x80x9d of the tooth-carrier respectively. This is complemented by a slightly convex structure, above all of the upper area of junction between the base or start of the nose of the tooth-carrier and the end or projection thereof which has a uniform section. The area of junction of the upper curved part of the nose of the tooth-carrier with the base thereof has a narrow flat transverse region. The lateral faces of the nose of the tooth-carrier assume the form of facets, one of them corresponding to the front projection of constant section and another to the lateral faces, which may be flat or gently curved with the convexity towards the outside.
With this arrangement the result is obtained that the nose of the tooth-carrier exhibits a much higher mechanical strength and, above all, in normal operation thereof no stresses are produced which tend to eject the tooth, which constitutes a recurrent problem of the currently known tooth-carriers. In particular, the slightly curved structure, with the convexity directed outwards, of the upper face of the nose of the tooth-carrier permits, in addition to a very efficient coupling between the tooth and the tooth-carrier, an increase in the cross-section of the nose of the tooth-carrier, and therefore a greater mechanical strength on the latter.
As described above, the upper surface of the tooth-carrier has an outwardly convex shape. Accordingly, the tooth cavity has a mirror image structure to allow the tooth to engage the tooth carrier. Thus, the upper surface of the tooth cavity has an inwardly concave shape. These shapes are illustrated in FIG. 13.
The device of the present invention is likewise characterized by a new type of cotter pin for retaining the tooth on the tooth-carrier, which is distinguished by its easy introduction and high resistance to removal, basically comprising a body of the cotter pin of flattened generally parallelepipedal structure, which on one of its intermediate sized faces has a wide rebate to which there is joined, by means of vulcanization of a special rubber, an insert carrying a small lateral projection with rounded transverse edges which is intended to be introduced into a seating of complementary shape of the tooth-carrier after its introduction.